1. Field of the Invention
The present invention relates to the structure of a cooling water path in an internal combustion engine, particularly to the structure of a cooling water path providing an improved cooling performance.
2. Description of the Prior Art
In a conventional auto internal combustion engine, for example in a four-cylinder engine, the cooling water runs through No. 1 cylinder block to the head, through the No. 2 cylinder block to the head, through the No. 3 cylinder block to the head, and through the No. 4 cylinder block to the head, which are independent of each other; and the cooling water, which flows into the cylinder, goes out of a cooling water hole installed at the front or the rear of the cylinder head. In this arrangement the cross-sectional areas of the cooling water holes provided for the cylinders within the cylinder head are about equal each other. Thus the cooling water runs fast at the end of the cylinder head located most downstream, but runs very slow at the end of the cylinder head located most upstream. As a result a number of stagnation areas occur where the flow is slow and they decrease the cooling performance, which may lead to a generation of hot spots in the cylinder wall and cause knocking in the engine. Moreover an uneven temperature distribution in the cylinder head and block may develop strain, resulting in a cracking of a cylinder head if it is exposed to a particularly high temperature.